1. Field of the Invention
The present invention relates to a plasma display apparatus and a driving method thereof
2. Background of the Related Art
Generally, a plasma display apparatus comprises a plasma display panel in which barrier ribs formed between a front panel and a rear panel constitute a single unit cell. Each cell is filled with a main discharge gas, such as neon (Ne), helium (He) or a mixed gas (Ne+He) of Ne and He, and an inert gas comprising a small amount of xenon Xe. When those gases are discharged by a high frequency voltage, the inert gas generates vacuum ultraviolet rays and radiates a phosphor material formed between the barrier ribs, thereby achieving an image.
FIG. 1 is a view illustrating a structure of a general plasma display panel.
In the plasma display panel shown in FIG. 1, a front panel 100 in which a plurality of sustain electrode pairs consisting in pairs of scan electrodes 102 and sustain electrodes 103 in pairs is disposed on a front substrate 110 for displaying an image and a rear panel 110 in which a plurality of address electrodes 113 intersecting the plurality of sustain electrode pairs is disposed on a rear substrate 111 are coupled in parallel at regular intervals to each other.
The front panel 100 comprises the scan and sustain electrodes 102 and 103 formed in pairs to discharge each other in one discharge cell and to keep the radiation of the cell. Each of the scan and sustain electrodes 102 and 103 is comprised of a transparent electrode ‘a’ made of an ITO (Indium-Tin-Oxide) material and a bus electrode ‘b’ made of metal. The scan and sustain electrodes 102 and 103 are covered with one or more dielectric layers 104 for limiting discharge current and insulating the electrode pairs from each other. A protective layer 105 deposited by magnesium oxide (MgO) is formed on the dielectric layers 104 to facilitate a discharge condition.
Barrier ribs 112 in a stripe or well shape are disposed in parallel in the rear panel 110 to form a plurality of discharge spaces, that is, discharge cells. One or more address electrodes 113 are disposed parallel to the barrier ribs 112 to cause an inert gas within the discharge cell to generate vacuum ultraviolet rays by performing an address discharge. An RGB phosphor 114 for emitting visual rays to display an image during a sustain discharge is coated on the upper surface of the rear panel 110. A dielectric layer 115 for protecting the address electrodes 113 is formed between the address electrodes 113 and the phosphor 114.
A plasma display apparatus for driving the above-described plasma display panel, a plurality of discharge cells is formed in a matrix type and drivers (not shown) having a driving circuit for supplying given pulses to the discharge cells are mounted.
In more detail, the plasma display apparatus comprises a controller for generating a control signal for controlling the plasma display panel upon receipt of an external image signal, a data driver for supplying a pulse to the address electrode by the control signal generated from the controller, a scan driver for supplying a pulse to the scan electrodes, and a sustain driver for supplying a sustain pulse to the sustain electrodes.
On the other hand, upon occurrence of charge and discharge in the plasma display panel, a driving pulse for driving the plasma display apparatus is generated by a switching operation of the respective drivers. As a result, an energy loss of the plasma display apparatus is increased and the temperature of a switching device is raised. Accordingly, the conventional plasma display apparatus comprises an energy recovering circuit for recycling an energy supplied to the plasma display panel, as illustrated in FIG. 2.
FIG. 2 is a view illustrating a conventional energy recovery circuit of the plasma display apparatus.
As shown in FIG. 2, the energy recovery circuit comprises a capacitive load Cp which acts as a load of the plasma display panel, an energy storage unit, i.e., a capacitor Cs for accumulating the energy recovered from the capacitive load Cp, an inductor L connected between the capacitor Cs and a scan or sustain driver 210 for applying a sustain voltage Vs, and first and second switches S1 and S2 connected in parallel between the capacitor Cs and the inductor L. Here, the sustain driver 210 is comprised of third and fourth switches S3 and S4 connected in parallel between the capacitive load Cp and the inductor L.
The operation of recovering and re-using energy of the above plasma display apparatus is as follows.
When the first switch S1 is turned on, a voltage Vs/2 stored previously in the capacitor Cs is supplied to the capacitive load Cp via the inductor L. At this time, a resonance circuit is formed by the inductor L, and thus a voltage Vs, approximately twice the voltage stored previously in the source capacitor Cs, is applied to the capacitive load Cp.
With the first switch S1 being turned on, when the third switch S3 is turned on, the sustain voltage Vs is applied to the capacitive load Cp, and the capacitive load Cp maintains the sustain voltage Vs during the turn-on of the third switch S3.
When the second switch S2 is turned on simultaneously with the turn-off of the first switch S1 and third switch S3, a current path extending from the capacitive load Cp to the capacitor Cs via the second switch S2 is formed, and thus the energy accumulated in the capacitive load Cp is recovered to the capacitor Cs, thereby accumulating a voltage Vs/2, approximately half the sustain voltage Vs, in the capacitor Cs.
When the fourth switch S4 is turned on as the second switch S2 is turned off, the capacitive load Cp continues to discharge until it reaches the ground voltage level GND.
Meanwhile, when the energy is recovered to the capacitor Cs, a malfunction or short-circuit may occur in the second switch S2. At this time, a voltage continues to be applied to the capacitor Cs through the second switch S2, and thus an excessive energy is accumulated in the capacitor Cs, thereby overheating and destroying the capacitor Cs. Further, the stability of the circuit deteriorates due to damage to the capacitor Cs.
Moreover, in the event of a short-circuit in the capacitor Cs, the energy cannot be accumulated in the capacitor Cs, thereby increasing power consumption in the plasma display apparatus.